The bow thruster generally is ineffective at（）.

Structural bulkheads on a ship are usually（）.

A.continuous
B.watertight
C.transverse
D.non-watertight

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Signs of racking stresses generally appear at the（）.

A.bow and stern shell frames and plating
B.junction of the frames with the beams and floors
C.garboard strake，at each side of the keel
D.thrust bearing of the main shaft

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